Generally, a magnetic recording medium such as a magnetic disck, a magnetic tape, etc., is produced in such a manner that a magnetic film forming liquid containing ferromagnetic fine particles dispersed in a bonding agent dissolved by a solvent is applied onto a belt-like non-magnetic support while continuously longitudinally conveying the support, the applied liquid is dried to harden, and the support is stamped out or cut.
In producing a magnetic tape, however, it is necessary to arrange the magnetic particles in the running direction of the non-magnetic support to increase the square ratio (the amount of residual magnetization Br divided by the saturation magnetization Bm) of an applied magnetic film, in order to increase the sensitivity of the tape to thereby improve the S/N ratio of the same. Accordingly, in the case of producing a magnetic tape, or the like, conventionally, there has been used a method in which a magnetic field in the conveying direction of a non-magnetic support is applied by a permanent magnet or a solenoid onto an applied liquid film before the applied liquid film has dried, so as to make the direction of the easily magnetizing axis of the magnetic particles agree (orientate) with the running direction of the support.
In producing a magnetic disk, on the other hand, if ferromagnetic fine particles are arranged in a specified direction during the production of the magnetic disk so as to produce an anisotropy in the magnetic medium, an anisotropy is generated also in each of the magnetic characteristics and electric characteristics in various directions. For example, if the magnetic particles are arranged in the direction of application of a magnetic forming liquid (that is, in the running direction of the non-magnetic support), the level of a reproducing output signal becomes higher in the direction of application of the magnetic film forming liquid than those in the other directions, so that the reproducing output signal level read out from the magnetic disk varies in accordance with the rotation of the disk. This phenomenon is generally called "modulation". Accordingly, in the case of producing a magnetic disk or the like, conventionally, there has been used a method in which a magnetic field is applied to an applied magnetic film forming liquid before the applied liquid has dried in a manner so as to disorder or randomize the orientation of the magnetic particles, in order to solve the above-mentioned problem that linearity occurs in the magnetic particles due to the fluid orientation in applying the magnetic film forming liquid.
Recently, there has been a strong demand to increase the memory capacity of magnetic storage means, that is, magnetic disks or magnetic tapes.
In order to increase the memory capacity, needless to say, the recording density per unit area of the magnetic recording medium must be increased.
Further, in order to increase the recording density, the writing magnetic flux generated from a magnetic head must be concentrated into a minute area, and therefore the magnetic head is miniaturized so that the amount of magnetic flux generated by the head decreases. Accordingly, the volume of the magnetic recording layer in which the direction of magnetization can be reversed by the thus decreased minute amount of magnetic flux is also decreased, so that it is impossible to produce complete reversal of magnetization unless the magnetic recording layer is decreased in thickness.
In order to satisfy the requirements as described above, accordingly, it becomes necessary to make the magnetic recording layer thinner.